Talks led by the U.S. Chamber of Commerce and the AFL-CIO over a new guest-worker program for lower-skilled immigrants are stalled, prompting members of the bipartisan group of eight senators to get personally involved to try to nudge the negotiations toward a resolution.

Business and labor groups have been meeting for weeks in an attempt to put together a system that would allow employers to find foreign labor when American workers are not available and that would allow foreign workers into the country. The idea is to create a new “W” visa category for lower-skilled guest workers. No such visas exists right now, leaving a vacuum that undocumented workers have been filling.

But the two sides have so far been unable to resolve their differences on a variety of points, chief among them the questions of how many visas would be awarded and what kind of workers would be eligible.

A union proposal obtained by CQ Roll Call includes language that would make occupations covered by the Davis-Bacon Act ineligible for the new program. That means that building contractors working under federal contracts would not be able to hire foreign workers under the program.

The Davis-Bacon law, which sets wage rates for contractors, has been unpopular with conservatives, and it’s unlikely that congressional Republicans would agree to those conditions, making it more difficult to reach a consensus. A chamber spokeswoman said that the business group would not agree to the provision.

The question of guest workers has been controversial in the past and was one of the main sticking points that sunk the last immigration overhaul effort, in 2007. This year, Sen. Charles E. Schumer, D-N.Y., a member of the bipartisan working group, said he preferred to outsource those talks to the business and labor representatives, freeing up time for senators to discuss other aspects of immigration policy.

The chamber and the AFL-CIO put out a joint statement last month outlining the points on which they had reached agreement. The statement was silent on some of the most difficult questions, and the two sides have yet to resolve those issues.

Although sources on both sides say the talks are ongoing, the negotiators have come to the conclusion that they will not have a fully formed program to present to the Senate group, which hopes to unveil its immigration bill in April.

“The idea that we were going to negotiate a final bill and present it as a baked cake was a little bit unrealistic,” said Randel K. Johnson, the chamber’s senior vice president for labor and immigration.

The sticking points remain the same as they’ve always been. One of the main areas of disagreement concerns how many new visas should be issued. The chamber, while it would prefer an uncapped program, agreed to set the ceiling at 400,000 visas per year, Johnson said. Labor, in order to protect American workers from competition, wanted an annual cap of about 10,000. That number would ebb and flow based on economic conditions.

Business groups insist that employers should be able to hire foreign workers once they’ve exhausted all possibilities of finding American workers. The number of guest workers allowed into the country should be determined by employer demand, they say, rather than by government officials.

Labor, on the other hand, wants the program to rely on detailed unemployment data, which will let the government determine how many workers to bring into the country.

“There’s no question it’s going to be a government system,” a labor source said. “We don’t want random employers to be able to game the system.”

The joint statement in February called for a new bureau to compile data on labor shortages as a way to determine where new workers might be needed. The two sides still disagree, however, on how much authority the bureau should have. Should it be involved in setting visa numbers or should it play a more advisory role?

The two sides are also discussing how wage rates for guest workers should be set. They have also talked about the categories of workers that will be covered under the new program but appear to have agreed to limit it to workers in jobs that do not require more than a high school diploma, the labor source said.

Despite their differences, the two sides have agreed on a few significant points. First, employers seeking foreign workers would have to apply for government certification, requiring them to prove they’ve exhausted all efforts to hire Americans. Workers, once hired, will be able to quit their jobs without fear of deportation and apply for new jobs from certified employers. Right now, in many visa categories, workers are dependent on employers for their visas, making them less likely to complain about employer abuse.

Business and labor also agree that guest workers should have a way to eventually earn legal permanent residence and, ultimately, citizenship, if they stay out of legal trouble and become enmeshed in American society.